In a statement, Sir Nicholas Lyell attacked the 'fundamental misconceptions' and 'myths' created by the media, including that Public Interest Immunity certificates were 'gagging orders'.
The idea that ministers who signed them in the Matrix Churchill case were 'thereby suppressing documents to save themselves while risking the defendants going to jail is utterly untrue', he said.
'My task as Attorney General is to act scrupulously and with complete integrity. I believe I have done so throughout.' He said his instructions to ministers was based on legal advice from two experienced barristers, advice which had subsequently been supported by Court of Appeal decisions.
A House of Lords ruling in 1967 established that, except in a 'clear case', the balancing of the public interest in maintaining Whitehall confidentiality against the interests of justice, was a matter for the courts, not ministers, he claimed. On this point Sir Nicholas found himself pressed by Lord Justice Scott and Presiley Baxendale QC, the inquiry counsel.
Asked to explain ministers' role in more detail, he insisted that all they were required to do when claiming PII in a criminal case was determine that documents fell into a category entitled to protection. Prosecuting counsel, not the minister, decided the relevance of the documents to the case.
Lord Justice Scott asked: 'The minister is the custodian of the public interest. If in relation to his documents he doesn't really mind whether they are disclosed and he doesn't think there is going to be any damage to the public interest that matters, then why should he claim PII. What is the point?'
Sir Nicholas was questioned on the way intelligence officers - whose evidence is normally protected - were allowed to appear for the prosecution, while ministers sought to deny the defence access to intelligence papers.
'The prosecution doesn't seem bound by the PII rigours in the same way the defence is,' Lord Justice Scott said. But Sir Nicholas defended a decision by the Chancellor, Kenneth Clarke, then Home Secretary, to permit an MI6 officer to give evidence. It was consistent with the 'clear case' exception.
The problem lay with PII practice, not the legal principles behind them. The law was even- handed between defence and prosecution. Sir Nicholas admitted he had not read the papers in the Matrix Churchill affair and did not know until the trial that one of the defendants worked for MI6.
He accepted that a lack of scrutiny by law officers may have meant the PII net was cast too wide in 'an abundance of caution and excessive secrecy' and the system needed to be improved.
The inquiry continues today.
Leading article, page 17